JPS6316126Y2 - - Google Patents

Description

[Detailed description of the invention] The invention relates to an electromagnetic focus type cathode ray tube.
In particular, the focus and center of the beam can be adjusted reliably and easily.

Unlike electrostatic focus type cathode ray tubes, which focus the beam, focusing is performed by utilizing the fact that electrons moving in different orbits converge at a predetermined point at a predetermined moment. Therefore, there is almost no beam repulsion effect, and essentially high resolution can be achieved. Moreover, if permanent magnets are used, power consumption can also be reduced.

However, conventional electromagnetic focus type cathode ray tubes have problems with focus adjustment and operability.
At present, the electrostatic focus type is mainly used. Here, we will first briefly consider the problems with focus adjustment and operability.

As is well known, a magnetic field lens system is equivalent to an optical lens system, and the thin lens formula can be used here as well.

f=1/a+1/b... In the formula, f is the focal length, a is the object point distance, and b is the image point distance. The object point can be thought of as the crossover point of the cathode lens system. The focal length f of the magnetic field lens system is given by the formula.

f=0.0221/V∫ ^∞ _X0 B(x) ² dx... In the formula, V is the high voltage and B(x) is the magnetic flux density distribution on the central axis. Each unit is [V],
It is [G].

By the way, when considering the magnetic flux density distribution of a permanent magnet, an expression can be obtained from Ampere's law of circular integrals.

∫ ^∞ _-∞ B(x)dx=0... If this is shown in a diagram, it will look like Figure 1, where the distribution of the lower edge (negative edge) continues gently to infinity. Such stray distribution causes noise to the deflection coil, etc., and also poses a problem in terms of focus. Therefore, in a magnetic field with such a stray distribution, it is desired that the distribution be as steep as possible.

On the other hand, for convenience, the magnetic field distribution shown in FIG. 1 is replaced with a bell-shaped magnetic field distribution shown in FIG. 2. This distribution is expressed by the formula.

B(x)=B _n /1+(x/λ) ² ... In the formula, λ is the half width and B _n is the maximum value.

Then, by substituting the equation into the equation, we obtain 1/f=0.0345λ/VB _n ^{2 .} . . From this equation, it can be seen that the focal length f and the half width λ are in an inversely proportional relationship (Fig. 3). Now,
The dimensions of the cathode ray tube are determined, resulting in a focal length f
is determined, and the magnetic flux density distribution is also determined. In this case, as shown in Figure 3, if the half width λ is large,
Since the variation Δf of the focal length f with respect to the variation Δλ is small, the depth of focus becomes deep and focus adjustment becomes reliable and easy. In this case, it is preferable to increase the half-width λ, which conflicts with the above-mentioned requirement to minimize the stray distribution. From this,
Previously, the complexity of focus adjustment remained a problem.

If the magnetic field distribution is as shown in FIG. 4, the stray distribution will not be a problem, and the half-width λ can be made large, and as a result, focus adjustment can be performed reliably and easily.

After intensive research, the inventors of the present invention were able to form a more preferable magnetic field distribution, solve both the stray distribution problem and the focus problem, and provide a cathode ray tube that makes it easy to adjust the center of the beam. Ivy.

Hereinafter, the fifth embodiment of the cathode ray tube of the present invention will be explained.
Let's explain with reference to the drawings that follow.

In FIG. 5, 1 is a panel, 2 is a funnel, and 3 is a neck tube, and a deflection coil 4 is mounted across the funnel 2 and the neck tube 3. A cylindrical member 5 is attached to approximately the center of the neck tube 3, and annular permanent magnets 6, 7 are attached to this cylindrical member 5. In this case, since the permanent magnets 6 and 7 are arranged outside the network tube 3, there is a high degree of freedom in design, and therefore the image magnification m
(=b/a) can be made as small as 5, for example. In general electromagnetic focusing, the degree of freedom is low because the electrodes are arranged inside the network tube 3, and is about 10 at most.

Note that 8 is a sealing metal part of the electron gun, and its diameter is generally larger than the outer diameter of the network tube 3. In this example, the former is 6.2 mm and the latter is 7.2 mm.

The cylindrical member 5 is specifically constructed as shown in FIGS. 6 and 7. 6 and 7, one end of the cylindrical member 5 has a deflection coil receiving portion 5a.
is formed, and a male threaded portion 5b is formed at the other end. This male threaded portion 5b has a plurality of (four in this example)
2) slits 5c are formed with one end open. The inner diameter of the cylindrical member 5 is such that the sealing metal part 8 of the electron gun of the network tube 3 can be inserted therethrough, and a protruding part 5d is formed at the tip of the male screw part 5b.

The annular permanent magnets 6 and 7 are inserted into the cylindrical member 5 with their north poles facing each other (FIG. 5), and then the female adjusting member 9 is screwed into the male threaded portion 5b. This screwing can be easily accomplished by cutting a knurl 9a (FIG. 8) on the outer periphery of the female screw member 9.
In this case, a repulsive force is generated between the permanent magnets 6 and 7,
Due to this repulsive force, the permanent magnets 7 and 6 strongly abut against the deflection coil receiving portion 5a and the adjusting female screw member 9, respectively. Then, due to the drag force at this time, a frictional force is generated between the permanent magnet 7 and the deflection coil receiving portion 5a. Similarly, a frictional force is generated between the other permanent magnet 6 and the adjusting female screw member 9.

In this example, the inner diameter of the permanent magnets 6 and 7 is the same as that of the cylindrical member 5.
The permanent magnets 6 and 7 can be made eccentric in the vertical and horizontal directions with respect to the cylindrical member 5, as shown by the arrows in FIG. The figure shows the case where it is eccentrically upward. As a result, the center of the beam can be adjusted by adjusting the positions of the permanent magnets 6 and 7. This adjusted position is then temporarily fixed by the above-mentioned frictional force. After the adjustment, the permanent magnets 6 and 7 are sealed with adhesive for final fixation.

The cylindrical member 5 is fixed to the neck tube 3 using a female screw member 10 for attachment. That is, the female screw member 1
The threaded portion 10a of 0 is tapered so as to become narrower toward one end (near the electron gun). As a result, when the female threaded member 10 is screwed deeply into the male threaded portion 5b of the cylindrical member 5, the protruding portion 5d of the cylindrical member 5 pinches the neck tube 3, and as a result, the cylindrical member 5 and the neck tube 3 are are integrated.

In such a configuration, the permanent magnets 6 and 7 form magnetic flux distributions as shown by solid lines and broken lines in FIG. 10, respectively. In this figure, l is the permanent magnet 6,
It is a gap of 7. And permanent magnets 6, 7
The resultant magnetic flux distribution is shown in FIG. 12. In the magnetic flux distribution of this example shown in this figure, the stray distribution component is a few percent (10% or less) of the total, and even if the half-width is large, the problem caused by the stray distribution is extremely small. Therefore, the half width can be increased to easily and reliably adjust the focus of the beam, and there is no problem with dropout.

It is unnecessary to explain that the beam focus adjustment described above can be performed by adjusting the screwing depth of the adjusting female screw member 9.

On the other hand, the center of the beam can be adjusted by manipulating the degree of eccentricity of the permanent magnets 6 and 7. Then, the lens system is displaced with respect to the optical axis, and the center position of the beam can be varied.

As mentioned above, according to the cathode ray tube of the present invention,
Since the annular permanent magnets 6 and 7 are attached to the outer periphery of the neck tube 3 with the same poles facing each other, an extremely preferable magnetic field distribution can be obtained, and as a result, focus adjustment can be performed easily and reliably. Moreover, this adjustment is made between the adjusting female screw member 9 and the cylindrical member 5.
This can be done easily by adjusting the depth of the screw engagement with the male threaded portion 5b.

In addition, since the permanent magnets 6 and 7 are attached to the cylindrical member 5 with a clearance, the permanent magnets 6 and 7
can be made eccentric with respect to the neck tube 3, and as a result, the center of the beam can be adjusted easily and reliably.

Further, the tapered female mounting thread member 10 is screwed into the male threaded portion 5b of the cylindrical member 5, and the neck pipe 3
Since the structure is such that the cylindrical member 5 clamps and presses the cylindrical member 5, and as a result, the two are integrated, the workability is extremely good. At this time, the slit 5c of the cylindrical member 5 can be used to make the clamping operation easier and more reliable.

Further, since the permanent magnets 6 and 7 are arranged outside the neck tube 3, there is a high degree of freedom in design, and the image magnification m can be made small. This, combined with the fact that the beam repulsion effect, which is a feature of electromagnetic focus, can be ignored, results in higher resolution.
Furthermore, since the aperture of the electromagnetic lens is increased, aberrations can be reduced.

Of course, by using the permanent magnets 6 and 7, lower power consumption can be achieved.

Note that the present invention is not limited to the above-described embodiments, and may take various configurations without departing from the gist thereof.

[Brief explanation of the drawing]

1 to 4 are diagrams for explaining the present invention, FIG. 5 is a side view showing an embodiment of the cathode ray tube of the present invention, and FIG. 6 is a partially cross-sectional view of the example shown in FIG. The illustrated side view, FIGS. 7 to 9 are perspective views showing the main parts of the example in FIG. 5, and FIGS. 10 to 12 are diagrams for explaining the example in FIG. 3 is a neck pipe, 5 is a cylindrical member, 5b is a male threaded portion of the cylindrical member 5, 5c is a slit in the cylindrical member 5, 5
d is a protrusion of the cylindrical member, 6 and 7 are permanent magnets, 9 is an adjustment female screw member, and 10 is a mounting female screw member.

Claims (1)

[Scope of utility model registration request] In a cathode ray tube, the beam is focused by attaching a pair of annular permanent magnets with the same poles facing each other to a cylindrical member provided on the outer periphery of the tube.
A male threaded portion is formed in the cylindrical member, and an adjusting female threaded member is screwed into the male threaded portion so that the distance between the pair of annular permanent magnets can be varied to adjust the focus of the beam; The inner diameter of the annular permanent magnets forming the pair is larger than the outer diameter of the cylindrical member, and the annular permanent magnets are made eccentric so that the center of the beam can be adjusted. A slit is formed through the electron gun in the cathode ray tube body, and a fixing female screw member with a tapered female screw portion is screwed into the male screw portion to secure the cylindrical member to the neck tube with clamping pressure. A cathode ray tube characterized by: